Rotary machines used in, for instance, industrial compressors, turbo refrigerators, small gas turbines, etc. are equipped with an impeller in which a plurality of blades are mounted on a disk fixed to a rotary shaft. These rotary machines rotate the impeller to give pressure energy and kinematic energy to a gas.
As the above impeller, a so-called closed impeller in which a cover is integrally mounted on the blades is known. This closed impeller may have a structure in which a plurality of parts are joined and assembled. When the impeller has this joined structure, there is a tendency for quality of shape in flow passages and performance of the impeller to decrease. For this reason, the impeller is made in one piece. However, when the impeller is made in one piece, complicated cutting and welding are required, and it takes time to assemble the impeller.
In Patent Literature 1, a technology in which a first member in which a disk section, a blade section, and a cover section that form flow passages are made in one piece and a second member located at one side of the disk section in an axial direction are separately formed, and thereby accessibility of machining tools to the first member can be improved is proposed.